666685 has 4 divisors (see below), whose sum is σ = 800028. Its totient is φ = 533344.

The previous prime is 666683. The next prime is 666697. The reversal of 666685 is 586666.

666685 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 488601 + 178084 = 699^2 + 422^2 .

It is a cyclic number.

It is not a de Polignac number, because 666685 - 2¹ = 666683 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (666683) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 66664 + ... + 66673.

It is an arithmetic number, because the mean of its divisors is an integer number (200007).

2⁶⁶⁶⁶⁸⁵ is an apocalyptic number.

It is an amenable number.

666685 is a deficient number, since it is larger than the sum of its proper divisors (133343).

666685 is a wasteful number, since it uses less digits than its factorization.

666685 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 133342.

The product of its digits is 51840, while the sum is 37.

The square root of 666685 is about 816.5078076785. The cubic root of 666685 is about 87.3588472484.

The spelling of 666685 in words is "six hundred sixty-six thousand, six hundred eighty-five".